Apparatus for enameling wire



,July 14, 1942. c. A. BAILEY 2,289,862

APPARATUS FOR ENAMELING WiRE Filed May 19, 1939 Inventor Carl A. BaiJeb5 WWCIJMA H is Attorne g- Patented July 14, 1942 APPARATUS FOR ENAMELING WIRE Carl AL Bailey, Scotla, N. Y., assignor to General ElectricCompany, a corporation of New York Application May 19, 1939, Serial No.214,554

8 Claims.

This invention relates to an apparatus for coating wire or othermetallic conductors with a liquid coating composition such as an enamel,varnish, lacquer or the like. The invention is especially concerned withthe application of viscous coating compositions to wire; such highlyviscous compositions including the product resulting from condensing analdehyde, such as formaldehyde, with a hydrolized polymerized vinylester, such as the hydrolysis product of polyvinyl acetate.

An object of my invention is to provide an improved apparatus forcoating wire-or other elongated metallic conductors with a uniformcoating of enamel or the like whereby the thickness of the coating canbe easily and definitely controlled.

Another object of my invention is to provide means for coating wire.with viscous resinous compositions of such viscosity in concentrationspractical for use in enameling wire, that they are not suitable forapplication by means of the usual type of wire-coating apparatus whichheretofore has been available.

A further object of my invention is to provide an improved combinationcoating-applicator and die which will not clog due to the presence oflint or other foreign matter on the wire and which can be usedadvantageously in connection with a horizontal baking oven.

' These objects are attained in accordance with the present invention bypassing the wire to be coated through a substantially triangularaperture or die formed by the grooves of a slowlyrotating grooved rollerand a spring finger pressing upon the roller surface and cooperatingwith the grooves to form said aperture.

In the accompanying drawing, Fig. 1 shows an apparatus partially incross-section with which my improved coating die may be used; Fig. 2 isa plan view of the coating means showing the improved die and itsrelationship to adjacent portions of the apparatus; Fig. 3 isacross-sectional view of the mechanism shown in Fig. 2 taken along theline 3-3; Fig. 4 is an enlarged view of a single V-grooved roller andthe cooperating spring finger showing the approximate position of thewire in the groove during the coating operation; Fig. 5 is amodification of my improved die structure.

Electrically insulated metallic wires wherein the insulation is of theorganic enamel type have heretofore been manufactured by passing thewire continuously through a bath of coating enamel, varnish or the like,and then vertically suitable source of power (not shown).

sheaves are capable of independent rotation on.

upward through a heated oven wherein the solvent is evaporated and thecoating material hardened. Although such practice proved satisfactoryfor coating wire with the ordinary oleoresinous varnishes, it is notparticularly suitable for the application of highly viscous materials.

In certain instances these highly viscous enamels or varnishes have beendiluted to the desired lower viscosity by the addition of appropriatesolvents. This practice, however, results in lowering the base contentof the enamel or varnish solution to such an extent that the resultingfilm is too thin to uniformly and completely cover the wire thusnecessitating the application of numerous coats with a correspondingincrease in cost of production when the wire travels through the bath ata reasonable rate. Furthermore, the use of these dilute solutions isattended by an increased loss of solvent during thebaking step and adecrease in the quality and quantity of the final insulating coating.

My invention not only eliminates the difiiculty heretofore encounteredin using viscous coating materials in an undiluted condition for thecoating of wire but also results in a uniformly coated wire wherein thecoating is of substantially equal thickness around the entirecircumference of the wire. It is particularly applicable to coatingsmall wire where any slight irregularity, caused for instance by thepresence of foreign matter, will not clog the die forming part of myinvention.

With reference to the drawing andin particular Fig. 1, the numeral Iindicates the wire or other metallic conductor which, as shown in thedrawing, is drawn from a pay-off reel 2 through an eyelet 3 and over asheave or group of sheaves 4. Sheaves 4, as shown in Fig. 2, are mountedon shaft 4a along with pulley. 5 which in turn is connected through belt6 and pulley I to a The shaft 4a in such a manner as to take up anyslack present in the wire without placing the wire under such tension asto cause breakage during operation of the device. The sheaves ordinarilyrotate at a slower speed than shaft 4a. After leaving the sheave 4, thewire I passes through coating device 8 described more indetailhereinafter. From the coating device 8 the wire enters oven 9 the wallsof which are provided with heat insulation Ill. The oven 9 i dividedinto upper and lower compartments by plate ll of stainless steel orother suitable material and is of such length that the coating isthoroughly hardened during the passage of the coated wire through theupper compartment and back through the lower compartment. An exhaust l2,provided in the upper compartment of oven I0, serves to remove thesolvent and other vapors from the interior of the oven during the bakingoperation. Heat is provided by heating elements I3 mounted in the lowercompartment of oven Ill. The coated wire after leaving the coatingdevice 8 passes through the upper and relatively cooler compartment ofoven 9 to return sheave or group of sheaves l4 after which it passesback into the oven and through the lower compartment in closerrelationship to the heating elements l3.

This arrangement permits a gradual increase in the temperature to whichthe coating material is subjected with a corresponding decrease in theformation of bubbles or other irregularities in the coating ordinarilycaused by too rapid baking and superficial hardening of the originallyliquid coating. Furthermore, by this arrangement, the maximum heat isapplied near the end of the heat treatment to thoroughly bake and hardenthe coating enamel or varnish after most of the volatiles have beenremoved. The apertures through which the wire I enters and leaves oven'9 are of such dimensions as to minimize the loss of heat from the oventhrough these openings.

After the wire leaves the lower compartment of oven 9 it is passedaround one of the sheaves 4 and through the coating device 8 and oven 8a sufficient number of times to obtain an insulating coating of thedesired thickness after which it is directed through eyelete 3a totake-up reel IS.

The coating device proper which is broadly indioated in Fig. 1 by thenumeral 8 is shown in greater detail in'Figs. 2, 3 and 4. This devicecamprises an overflow sump I6 of elongated rectangular shape on which issuitably mounted a well member or block II. The block I! is providedwith a T -shaped groove or well It containing the enamel or othercoating material which is introduced into this well through inlet pipel9 under a pressure head of approximately 7 or 8 inches of coatingmaterial. The well l8 need not be of the particularcross-sectional shapeshown but may vary in shape so long as it accommodates the receptacle 20which, as

shown in Fig. 3, is sweated into the upper part of the T-shaped well.The receptacle 20 which is shown as being of semi-circular cross-sectionis provided at the bottom with a number of apertures 2| through whichthe enamel enters the receptacle from the well l8 due to the slightpressure head on the enamel or varnish supply.

Within receptacle 20 and extending the entire length thereof isrotatably mountedha rolle'rfion cylindrical rod 22 in such a position asto dip into the enamel supply entering receptacle 20 through apertures2|. Any excess enamel overflowing the edges of the receptacle 20 flowsinto the sump I 6 either through overflow trough 23 and drains 24connecting this overflow trough with sump IE or directly to sump l6'over beveled edge 25 of member IT. A return pipe 26 connected with sumpl6 carries this overflow back to the source of supply (not shown) andfrom there to suitable pumps, filters, etc. and finally 1 back throughinlet pipe [9 to well I'l.

The grooved roller or rod 22 is provided with a number of preferablyV-shaped groove 21 equal to the number of strands of wire passingthrough the apparatus. The slow rotation of this roller in the directionoftravel of the wire, transfers the coating material to the wire as thewire passes through the groove and at the same time carries any lint orother foreign matter away from the actual wire-coating zone. This modeof operation is particularly advantageous in the coating of small sizewire where, because of the comparatively small die opening, the presenceof even a small amount of foreign material around or in a fixednon-movable die opening will seriously impair the efllciency of theapparatus and unless removed immediately will result in a nonuniformcoating of the wire or even in the complete absence of coating materialon certain portions of the wire.

Spring fingers 28 are so mounted above the roller as to cooperate withthe V-grooves 21 to form a substantially triangular coating-die throughwhich wire I passes. These spring fingers, which are an importantfeature of my invention and which need not be of fiat rectan ular shapeas shown in the drawing but may be of any other suitable shape so longas that por-- to freely passthrough the die without injuring.

either the coated wire or the die members proper and as stated above anyforeign particles will be carried away from this coating zone by therevolving roller. The apertures 2|, previously referred to, are sospaced in the receptacle 20 that one aperture is provided for eachV-shaped groove 21 in roller 22.

One end of the spring fingers 28 i rigidly mounted on the inclinedsurface 29 on one side of member I! by means of bar 30 and set screw 3lA number of the bars 30 may be used depending upon the length of thecoating device as a whole. As shown in Fig. 2, bar 30 serves to holdfour of the spring fingers in place.

The wire I after leaving the sheaves 4 enters the coating device 8through slots or guides 32' each of which is in line with one of thegrooves 21 in roller 22 and with one of the sheaves 4. These slots orguides are of such width as to permit free movement of the wire, yetnarrow enough to insure proper alignment of the wire in grooves 21.

The grooved roller 22 may be a single rod havinga. number of V-shapedgrooves 21 machined.

therein or may be made up of a number of units each having a singleV-groove, said units being fixedly mounted on a shaft 33. This shaft inturn carries a pulley 34 which through the means of belt' 35 and pulley36 is driven from shaft 4a on which the sheaves 4 are mounted. Therelative speed of rotation of these roller units with respect to thespeed of travel of the wire may be controlled by changing the relativesize of the.

circumferential ridges or collars machined onto roller 22 during itsmanufacture support the roller 22 by bearing on the inner surface ofreceptacle 20 and also serve to prevent the enamel entering receptacle20 through apertures 2| from flowing" to one or the other end ofreceptacle 20 in the event that the device as a whole is not level. Theenamel or other coating composition collecting in receptacle 2!! betweenflanges 38 is transferred to the pools of coating material beneathspring fingers 28 by the rotation of roller 22.

Fig. 4 is an enlarged view of a portion of grooved roller 22 and spring28 showing the relative positions of the groove 21, spring 28 and wire Iduring the actual coating operation. The wire of circular cross-sectionbears lightly upon the V-shaped groove 21 at only two points, one oneach leg of the V. Ordinarily, the spring finger 28 bearing on thesurface of the roller does not come in actual contact with the wire I asit passes through the triangular-shaped aperture. This finger not onlycauses the formation of a small pool or bath of enamel behind the diethrough which the wire must pass but also removes any surplus enamelfrom the wire before it leaves the coating device and enters the oven 9.The quantity of enamel applied to the wire is determined by the depth ofthe V-shaped groove 21 in relation to the wire size and thus may becontrolled by changing the size of the groove.

It will be observed that as the wire leaves the die aperture it iscoated with three circumferentially spaced triangular-shaped portions ofenamel. These portions, particularly on small sized wires, readilycoalesce to form a layer or film of uniform thickness. In this respectmy coating device represents a substantial improvement over prior artgrooved roller coating devices wherein the groove is, of semi-circularcross-section having a radius of curvature equal to or greater than theradius of the wire. In using such semi-circular grooves a considerableportion of the bottom surface of the wire tends to drag on the bottom ofthe semi-circular groove with the resultant deposit of a large portionof enamel on one side of the wire and substantially no coating on theopposite side. The triangular or similar shaped aperture on the otherhand permits the application of a number of spaced portions of enamel tocertain regions about the circumference of the wire which can much morereadily flow together into a uniform continuous coating. Although I havedescribed the coating roller as being provided-with a substantially V-shaped die-forming groove, it is understood that grooves of varyingshape may be used in practicing the invention. For example, the bottomof the groove may be slightly rounded or curved so long as the radius ofcurvature is less than the radius of the wire. It may also be flattenedso long as the wire contacts the groove in the manner set outhereinbefore; that is, at certain isolated points between whichsubstantially equal portions of enamel are applied to the wire.

Fig. 5. shows a modification of my coating apparatus characterized bythe presence of a number of grooves for each strand of wire. In thismodification I preferably use a number of rollers, segments or spools llprovided with grooves 42a, 42b and 420 through one of which the wirepasses. Flanges 44 on these spools or rollers serve the same purposes asflanges 38 shown in Fig. 2. Spring finger 43 comparable to spring finger28 in Fig. 2 is then made of such width as to cover all of the groovesin one spool or roller. The center groove of the group of grooves, whichmay be of any number, is so positioned as to be substantially in linewith slot or guide 3| so that, ordinarily, the wire I is passing throughthe pool of enamel or other coating material collecting behind the dieopening formed by this particular groove and spring finger 43. However,in practice, an enlargement in the wire, caused for instance by a spliceor the presence of foreign matter, will sometimes cause the wire to jumpfrom this groove. By providing a number of closely spaced grooves ineach segment or unit of the rotating roller, I- prevent any seriousdamage to the coating as a whole since the wire will immediately fallback into either the original groove or one of the adjacent grooves dueto the spring pressure of spring finger 43. With a roller having onlyone groove per wire strand, there is the possibility that the wire willride the smooth surface of the roller near the groove for some timeafter jumping from the groove proper, thus resulting in a scrapingaction of the roller and spring finger on the wire and the accompanyinginjury or removal of the insulating enamel.

The size and depth of the grooves, as stated previously, are determinedempirically and will depend upon the size of the wire to be receivedtherein, the thickness of the coating desired, the viscosity of thecoating material, and other variables. The rotational speed of theroller need only be suificient to insure the transfer of an ample supplyof coating material to the wire and a ready removal of foreign materialsfrom the coating zone or die proper. L

- What I claim as new and desire to secure by Letters Patent of theUnited States is:

1. An apparatus for coating wire comprising a receptacle for coatingmaterial, a grooved roller mounted in said receptacle so as to bepartially immersed in said coating material, and a fiat spring memberbearing on the surface of said roller and forming with said groove acoating aperture adapted to receive the wire to be coated.

.2. An apparatus for coating wire comprising a container for coatingmaterial, a roller having a circumferential groove therein and dippinginto the coating material in said container, means for passing said wiretangentially through said roove at the top of said roller, and a springfinger bearing upon said roller and serving to confiwiiile said wire insaid groove during coating of the e. 3. In a wire-coatingdevice, acooting die comprising a V-grooved roller and a spring member, bearingon the grooved surface of said V-grooved roller and forming therewith atriangular-shaped opening adapted to apply a limited amount of coatingmaterial to a wire passing therethrough, said roller being so mounted ina bath of coating material as to convey said coating material to saidopening upon rotation of said roller.

4. A wire-coating apparatus comprising a receptacle for the coatingmaterial, a rotatable roller partially immersed in said coatingmaterial, said roller having a substantialy v-shaped groove therein toreceive a wire to be coated, and a fiex ible spring finger one end ofwhich is rigidly fixed to a suitable support and the other end of whichbears against the surface of said roller and forms with said groove asubstantially triangular-shaped coating aperture for the wire.

5. An apparatus for coating wire with viscous coating materialcomprising a coating-applying 78 rotatable grooved roller and a springfinger bearing on the arooved surface of said roller to form therewithan aperture to receive said wire.

6. An apparatus for coating wire comprising a grooved rotatable carrierfor a liquid coating material, means for supplying said coating materialto said carrier, means ior passing the wire through the groove of saidcarrier, and a member resting on the periphery of said rotatable carrierand cooperating with said groove to low an aperture for receiving thewire to be coated.

7. A wire coating device comprising 'a V- grooved roller, a iiat member,on end or which bears upon the surface oi said ro er and forms with thegroove a substantially triangular-shaped o ening for receiving the wireto be coated and means for supporting said roller and said flat membertor movement relatively to each other.

8. A die assembly for coating a metallic wire comprising, a rollerprovided with a circumierential groove. a. flat member bearingcon thesurface or said roller and means tor mountini said flat member formovement toward and away from said groove, said aroove and said memberiormina an aperture to receive the wire to be coated.

CARL A. BAILEY.

